I'm hating on HTC on this one. I saw plenty of articles and blogs over the past months clearly stating it would be a problem for the Hero. Then, if any of you recall, everyone lit up with info that HTC had added the Hero to the list. By name. By HTC. I can't find any of that anywhere now, just the rumor posts.

Key features of 2.2. A lot of which is in custom roms already, but I am not rooting my evo this time round. Froyo is too close, and i'm happy with it the way it is. Thank you snapdragon.

JIT (Just in time compiler) - increases linpack scores from 7-8 to 38 (saw in a youtube comparison running ported froyo)! Hero gets 2.5 average. Just know that thats a big difference! ( which means FAST!)
Apps2SD- install apps on your sd card allowing you to have more apps then that capable or installing on the phones internal disk
Flash- Of course this is good news, assuming it runs ok officially. Full flash support. No more flash lite. This means flash games, youtube videos on website without launched the player etc..
V8 Javascript - Faster internet, browsing.
Market- Auto updating apps or update all apps when your apps need updating

I'm sure those videos go into more detail, but these are the main improvements you will notice. I want my desert!